People who teach physics often remove friction from calculations to make life easier for students. While that might speed up someone’s homework, it does mean that this all-important force tends to fade into the background, despite it being crucial for our daily lives. Here to bring friction centre stage is Jennifer Vail, a “tribologist” – or studier of friction – at US firm TA Instruments.
Friction: a Biography is an engaging and wide-ranging book illustrating its many manifestations in the natural world, showing how this force can be harnessed to solve practical engineering problems. Vail, who wrote the book after giving a hugely popular TED talk on friction, does a great job of connecting abstract physical ideas with familiar human experience.
I like, for example, her description of what happens when two surfaces slide over each other but the friction between them isn’t constant. As she explains, this “stick-slip” motion isn’t great if you’re trying to inject a drug into someone with a syringe. But it can be exploited to beautiful effect by violinists, creating “downright lovely” sounds (though apparently not when she’s practising on her own viola).
One of the book’s strengths is its historical context. Famous figures like Leonardo da Vinci are introduced alongside the development of their ideas, lending a human dimension to the science. The author does a great job of explaining how tribology, which comes from the Greek for “to rub”, has been shaped by careful experimentation and the application of rigorous scientific thinking to industrial problems.
After a trip to Switzerland, the physicist Frank Bowden showed we can ski because frictional heating causes a thin layer of snow to melt beneath our skis, providing liquid lubrication.
After a trip to Switzerland, for example, the Australian-born physicist Frank Bowden showed we can ski because frictional heating causes a thin layer of snow to melt beneath our skis, providing liquid lubrication. This overturned an earlier explanation associated with Osborne Reynolds (best known for the eponymous number marking the transition from laminar to turbulent flow) who’d thought that snow melts due to pressure.
Then there is the 19th-century researcher Robert Thurston, whose pendulum experiments on friction in bearings, described here in detail, guided the design of more efficient lubricated systems. As Vail explains, understanding friction is vital in the design of engines, where even small modifications – such as texturing surfaces, adding coatings, or putting nanoparticles into lubricants – can make them much more efficient and extend their useful life.
Historical anecdotes are woven throughout the book. The story of why graphite in pencils came to be called “lead” is particularly memorable. It turns out that the Romans used lead to write, so the name stuck – even after graphite became more popular because it allowed darker writing. There are also lots of excursions into the natural world: did you know that beetles have a protein in their leg joints that acts as a solid lubricant?
Smooth operator
Vail’s discussion of lubrication is clear and well-integrated with practical examples. Particularly insightful is the explanation of how hydrodynamic lubrication occurs in biological systems, such as human cartilage, where a thin fluid layer separates cartilage surfaces in joints, reducing friction and wear. As Vail makes clear, tribology is vital in physiology, for example in how contact lenses work when we blink our eyes or how food feels in our mouth when we chew.
The book also examines fluid dynamics and drag, distinguishing between viscosity as a material property and drag as a force. Vail’s discussion of plaque on the walls of our arteries is particularly compelling. If there’s not enough drag to shear off the plaque it can cause blockages and, potentially, a heart attack – showing how friction plays a role in our health.
Environmental considerations are addressed too. The author discusses, for example, the impact of polytetrafluoroethalyene (PTFE), which she calls “the most controversial solid lubricant ever”. Also known as Teflon, it is widely used in frying pans, but is synthesized using some pretty nasty carcinogenic “forever” chemicals that don’t break down in the environment. PTFE also has a shady past, being first used in the Manhattan atomic-bomb project to coat valves when separating isotopes of uranium.
Friction can improve energy efficiency, reduce greenhouse-gas emissions, and mitigate global warming.
On a more positive note, Vail shows how an understanding of friction can improve energy efficiency, reduce greenhouse-gas emissions, and mitigate global warming. The book extends further still, encompassing atmospheric, oceanic and planetary processes, as well as astronomy and cosmology. Friction is a universal physical principle, extending well beyond conventional engineering applications and broadening the scope of the book.
However, Vail’s intended audience is not always clear. Some sections read like a primer for tribologists, while others are highly speculative, such as the idea that life originated on Earth because oxidized molybdenum was delivered from Mars aboard Martian meteorites. There are also occasional errors and ambiguities, such as her discussion of the subtleties of the Earth’s tides.
Statements such as electric vehicles “consuming 106% energy” could have been more clearly explained, while her market estimate for anti-friction coatings of just over $1.5m by 2028 is almost certainly too low by three orders of magnitude. While these issues do not undermine the book’s scientific substance, they may distract careful readers, and the rapid movement between topics occasionally disrupts the narrative flow.
Overall, though, Vail does a good job of balancing technical exposition with anecdote and gentle humour. Friction might seem an unpromising subject for a book, but non-expert readers will find much to surprise and engage them. Despite its flaws, I would recommend it as an illuminating, if imperfect, celebration of friction and its central role in science and engineering.
- 2026 Harvard University Press 248pp £23.95hb
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